ABSTRACT 



On the basis of a chromatographic analysis, Artemisia 

 tridentata is divided into seven subgroups: three of subspecies 

 vaseyana , three of subspecies tridentata , and one of sub- 

 species wyomingensis. The three subgroups included in A. 

 tridentata subsp. tridentata show low utilization by game and 

 livestock; the four subgroups included in subspecies vaseyana 

 and wyomingensis show high utilization, especially on winter 

 ranges. Although each subgroup occupies a distinctive ecolog- 

 ical habitat, few consistent morphological differences are 

 manifested, particularly among the subgroups of subspecies 

 vaseyana and subspecies tridentata . 



Chromatographic comparison of the species in the 

 section Tridentatae suggests that subgroup lie of A. tridentata 

 subsp. tridentata may have been the ancestral form to develop 

 from A_. biglovii. In turn, this form probably gave rise to the 

 remaining subgroups of A. tridentata and most other species 

 in this section. 



